We have partially purified from bovine scapular cartilage a growth factor which induces DNA synthesis and cell division in bovine chondrocytes and in Balb/c 3T3 cells. The growth factor is cationic and has a molecular weight of approximately 11,000 to 13,000 daltons. The biological activity of the growth factor is destroyed by trypsin digestion but not by incubation with 2-mercaptoethanol. Stimulation of cell division is accompanied by changes in cell morphology. We propose 1) to purify and characterize the growth factor; 2) to study the biochemical mechanism of action involved in the induction of cell proliferation; 3) to grow chondrocytes and Balb/c 3T3 cells in serum-free media containing growth factor as the mitogen; and 4) to investigate the role of the cartilage-derived growth factor in vivo in the growth and development of normal cartilage, in cartilage regeneration, and in cartilage showing abnormal patterns of proliferation such as occur in chondrosarcoma, osteoarthritis, and achondroplasia.